1. Field of the Invention
The present invention relates to sunscreen emulsion compositions that provide improved sunscreen protection to skin. The present invention also relates to a method of improving the sunscreen protection factor (xe2x80x9cSPFxe2x80x9d) of a sunscreen emulsion composition. Additionally, the present invention also relates to a method of providing a desired SPF to an emulsion composition using less sunscreen active(s).
2. Description of the Prior Art
Sunscreen compositions are available commercially in the form of emulsions with hydrophobic organic sunscreen actives in the inner discontinuous phase. Such emulsions are shown, by way of example, in U.S. Pat. Nos. 4,015,009; 4,024,106; 4,455,295; 4,613,499; 4,710,373; 4,863,963; 5,160,731; 5,338,539; 5,426,210; 5,783,173; and 5,917,088.
Heretofore, it has been traditionally accepted by those skilled in the art that highly stable emulsions (i.e., with small uniform droplet size) were necessary to produce sunscreen emulsions with high SPF. It has been observed that such stable emulsions require the use of relatively high levels of emulsifying agents, film formers and sunscreen actives. The prior art problem to be addressed is how to provide improved sunscreen protection products, preferably maximum sunscreen protection products, with a minimum amount of sunscreen active.
Thus, it is desirable to have a stable sunscreen composition in emulsion form that provides enhanced sunscreen protection with a lesser amount of a sunscreen active than previously possible.
It is an object of the present invention to provide a sunscreen emulsion composition that provides enhanced sunscreen protection.
It is another object of the present invention to provide a sunscreen emulsion composition that provides a given degree of sunscreen protection with a lesser amount of sunscreen active than previously possible.
It is another object of the present invention to provide a method of protecting skin from ultraviolet radiation and the damage (e.g., wrinkles, sunburn) associated therewith.
These and other objects and advantages of the present invention are provided in the present sunscreen composition by reducing the steric stability of a sunscreen emulsion compositions, i.e., by preparing a meta-stable emulsion. The emulsion has an inner discontinuous phase and an outer continuous phase. The inner discontinuous phase and/or outer continuous phase has at least one sunscreen active therein. The inner discontinuous phase is generally dispersed within the outer continuous phase in the form of discrete droplets having a multimodal droplet size distribution.